More precisely, the invention relates to the type of machine comprising a hopper for storing empty straws, a filling station for straws, as well as a transport device provided with elements for receiving and holding the straws and capable of conveying straws taken from the hopper to present them at the filling station.
Machines of this type are described for example in documents FR 2,700,313 and U.S. Pat. No. 4,478,261, according to which the transporter is a fluted rotating barrel, and CH 533,542, according to which the transporter is constituted by several likewise fluted mobile endless bands.
The grooves ensure reception of the straws coming from the hopper, their transfer to the filling station, and being held during filling.
The transporters function step by step, such that a straw, or a group of straws, is immobilised at the filling station during this operation.
Such a machine is generally adapted to filling straws whereof one of the two ends, known as distal, is blocked by a stopper initially permeable to air, but capable of becoming watertight when it is soaked in a liquid. The stopper is made for example from polyvinyl alcohol powder intercalated between two buffers of fibrous material.
The filling station comprises means for introducing semen at the opposite end, or “proximal” of the straws, as well as means for suctioning the semen via their distal end, through the porous stoppers.
On contact with the semen, or a certain quantity of non-spermicidal intermediary liquid, in keeping with the ideas of FR 2,810,535, the stopper hardens and becomes impermeable, tightly blocking the distal end.
Located downstream of the filling station is a closing station for the proximal end of the straws, this closing generally being completed by ultrasound welding.
After filling and closing, the straws are released from the transporter and collected in a receptacle ad hoc.
They are then frozen for later use.
Straws being used currently are fine cylindrical tubes, made of flexible and transparent plastic, such as PVC (polyvinyl chloride) in particular.
The majority of straws available on the market has a length of 133 mm, and there are two categories of straws of differing diameters, specifically straws having a diameter of the order of 2 mm (in practice 1.95 mm) and straws having a diameter of the order of 3 mm (in practice 2.85 mm).